While current drug therapies have dramatically increased the longevity and quality of life for AIDS patients, virological failure-the inability to maintain suppression of HIV replication-does occur. Much, but not all of this failure appears attributable to the development of antiretroviral resistance mutations.The reemergence of viremia can extend to the cerebrospinal fluid (CSF) suggesting new infection and/or reactivation of latent HIV infection within the brain. Indeed, it is often proposed that the brain serves as an important HIV reser voir. The mechanisms governing transcriptional regulation of HIV replication in brain, as well as reacti- vation of latent HIV infection, remain in question, this application targets these critical issues, particularly within the context of astrocyte-macrophage interactions. Under both normal and pathological conditions, these two cell types interact structurally, and functionally, in a myriad of ways. Also, both are susceptible to HIV infection, but differ significantly in the course of that infection. Macrophages support full-blown produc- -tive replication, while astrocytes develop a nonproductive infection, which can support transcription of the HIV accessory genes. In preliminary studies we have found that tat and nef expressed within astrocytes can trigger HIV expression from latently-infected macrophages, that tat expression in astrocytes leads to upregulation of the endothelin-1(ET-1) gene, and that ET-1 is regulated at the transcriptional and translat- ional level in astrocytes by tat, gp120 and HIV infection. ET-1 is a potent vasoconstrictor involved in isch- emia, disruption of the blood-brain barrier and neuronal death, which has been little studied in the setting of HIV brain infection. Based on these and other observations we propose to (1)examine HIV accessory gene transcription in astrbcytes and determine if, and how, this transcription can lead to activation of latent HIV infection in macrophages and role in ET1 induction,(2)examine HIV-mediated induction of ET1 in astrocytes and macrophages and (3) determine the effects of statins on ET1 regulation in HIV-infected astrocytes and macrophages. These studies will utilize both primary cells and neoplastic cell lines stably transfected with HIV accessory genes, HIV reporter systems or ET-1 promoter constructs. Astrocyte-macrophage interact- ions will be mimicked using coculture systems. This work should significantly advance our understanding of the regulation of HIV replication and expression in brain, particularly the reactivation of latent infection.